The present invention generally relates to management of a storage apparatus.
As an example of a logical volume, there is a virtual volume as disclosed in Document 1. The virtual volume is provided with a plurality of address ranges. In the case in which an address range is a write destination, a physical area (a physical storage area) is allocated from a pool to the address range, and a write target data is written to the allocated physical area. As a result, a real storage capacity of the virtual volume is dynamically extended. In the case in which an allocation to an address range of the allocated physical area is canceled, the physical area becomes an unused physical area.
An amount of change per unit time for a used capacity of a pool (the total storage capacity of the allocated physical area) is dynamically different depending on a trend of an access to a virtual volume. Consequently, a certain amount of extra storage capacity is ensured for a pool.
However, depending on a trend of an access, a used capacity of a pool is not increased so much, and therefore, a storage capacity ensured for a pool includes a useless storage capacity in some cases.
For instance, Document 2 discloses a technique in which a trend of an increase for a used capacity of a pool is figured out corresponding to a request for creating a volume and a storage capacity that was judged as being useless at some point in time is used as a capacity of a volume to be created.    [Document 1] Japanese Patent Application Laid-Open Publication No. 2003-15915    [Document 2] Japanese Patent Application Laid-Open Publication No. 2007-241593